Abstract: During the factory test run, the raceway of a turboprop engine reducer gear shaft peeled off. The reasons for spalling of the gear shaft raceway were analyzed by means of macroscopic observation, magnetic particle testing, scanning electron microscope analysis, grinding burn inspection, metallographic examination and hardness test. The results show that the contact fatigue spalling occurred on the gear shaft raceway, and the grinding burn area existed on the working surface of the raceway, which reduced the contact fatigue strength and produced fatigue cracks, and finally led to the spalling of the gear shaft raceway.